Is this really a possibility to begin with? What are the odds of Tokyo needing to be evacuated in the first place? It's just the media taking things out of proportion as always. Have there been any signs of dangerous levels of radioactivity anywhere near Tokyo at all?
After what I've read thus far the radiation levels are quite a bit far from being strong enough to have an direct impact on Tokyo. Not to mention all weather reports I've seen lately shows wind blowing towards the sea and away from Tokyo and not towards the city?
All this makes it highly unlikely that Tokyo will get effected by the radiation in any critical or major degree? So why would you evacuate and start a mass-panic in a city of this size, with so many inhabitants if the possibility of disaster is so unlikely? Wouldn't a mass evacuation of a city with so many people in it most likely damage the city and the people more than the radiation itself at it's current state?
If there wore to be a complete meltdown of the reactor core(s), and the radiation would leak straight out into the atmosphere and the wind brought it straight at Tokyo I guess it would be too late to evacuate the city but the Japanese government have to reconsider the possible downsides of a evacuation and compare it to the current risk of heavy radiation hitting Tokyo and currently things are pointing towards Tokyo being left okay doesn't it?